Reduction of baseline fluctuation in Electrocardiogram measurement for a car driver

Baseline fluctuation in Electrocardiogram (ECG) measurement system for car drivers is analyzed. The goal of this research is to develop a system that detects changes in R-R interval fluctuation, which is related to drowsiness and stress of the driver, and alert the driver to prevent drowsy driving. This system measures ECG with a contact electrode on the steering wheel and a capacitively coupled electrode on the driver´s seat. This configuration allows ECG measurement while the driver is holding the steering wheel with one hand. The major source of baseline fluctuation is the static electricity generated by body motion, especially the pedaling motions that involve contact and removal of foot on the pedal. Baseline fluctuation can be as large as hundred times of the R-wave amplitude. Analysis of equivalent circuit model and experiments have shown that the baseline fluctuation can be reduced to 0.05 V by introducing an additional electrode on the driver´s floor and connect it to the electrode in the steering wheel.